While scoring the sci-fi action film Looper, which stars Bruce Willis and Joseph Gordon-Levitt, composer Nathan Johnson employed some unusual instrumentation. One of his primary sound effects was an industrial fan, which he recorded during a trip to New Orleans, and he used several other instruments that he built himself for an otherwordly effect. In this behind-the-scenes video, Johnson explains his recording process and unconventional decisions for the score.

Looper hits theaters on September 28th; its soundtrack is available for pre-order on iTunes.